1. Field of the Invention
This invention relates generally to burglar alarm systems and more particularly to a self-contained monitor surveiling a predetermined space in a premises for an occurrence of an intrusion. The self-contained monitor includes a memory circuit which may be remotely tested by a returning occupant to determine if an intrusion has occurred in the predetermined space.
2. Description of Related Art
Burglar alarm systems comprising a self-contained intrusion monitor used to surveil a predetermined space and a remote controller employed to control the self-contained monitor are well known in the art. In such systems, the monitor typically includes a motion sensor and a memory circuit. The motion sensor detects an unauthorized entry into the predetermined space in a premises such as an apartment or a house and the memory circuit records the occurrence of the intrusion. Before reentering the premises, a returning occupant manipulates the remote controller to prompt a response from the self-contained monitor to determine if an intrusion has occurred and whether it is safe to enter the premises.
U.S. Pat. No. 5,621,385, issued to William P. Carney on Apr. 15, 1997, teaches an alarm system comprising a self-contained monitor and a hand held remote controller. The monitor, powered by either batteries or by an AC power line transformed and rectified to supply a DC potential, surveils a predetermined space, initiates an alarm as a result of an intrusion into the space and records the occurrence of the intrusion. Carney""s system provides a reliable RF signalling protocol which enables an authorized user to remotely arm, disarm or test the monitor for the intrusion without causing a false test report through misuse of the remote controller. Should the monitor sense either an intrusion or a power interruption, it does not respond to an RF test signal thereby warning the occupant not to reenter the premises to avoid the possibility of encountering a remaining intruder. Carney""s system reports all sensed power interruptions as having been caused by an intrusion. His disclosure does not teach a self-contained monitor that minimizes the number of intrusion reports caused by faults which frequently occur on an AC power line that are not a result of an intrusion. False intrusion reports are a significant problem and inconvenience for a returning occupant who needlessly seeks help based on the lack of a monitor response which was caused by a power line fault rather than by an actual intrusion.
U.S. Pat. No. 5,808,547 which issued to William P. Carney on Sep. 15, 1998 as a Continuation-in-Part (CIP) of the above referenced U.S. Pat. No. 5,621,385 teaches an alarm system comprising a battery powered hand held remote controller and a self-contained monitor energized by either batteries or an AC adaptor cord. The self-contained monitor includes an intrusion detector for sensing an intrusion and a memory circuit being switched from an armed state to a disarmed state by a sensing of either an intrusion or a power interruption to the monitor. The CIP teaches a remote controller which employs a unique RF signaling protocol to arm, disarm and test the monitor for an occurrence of either an intrusion or a power interruption. If the monitor senses either the intrusion or the power interruption it does not respond to an RF test signal. The CIP teaches that all sensed power interruptions are reported as having been caused by an intrusion. The lack of a response to the RF test signal warns a returning occupant that an intrusion may have occurred and there exists the possibility of confronting a remaining intruder should he or she enter the premises. Carney""s signalling protocol enables the returning occupant to repeatedly test the monitor to be sure of its response before engaging in what may be a time consuming and stressful effort to seek help. Carney does not address the problem of false intrusion reports being produced by the monitor because AC power line faults occurring on the AC line supplying power to the monitor switched the memory to the disarmed state.
U.S. patent application Ser. No. 09/372,836, filed by William P. Carney on Aug. 12, 1999, teaches an intrusion alarm and detection system. The system defines a self-contained monitor for sensing and recording an intrusion and a remote controller employed by a user to arm, disarm and test the monitor by transmitting a coded RF signal thereto. The monitor includes a primary power source comprising either an AC power line or batteries, a nonvolatile memory circuit for secreting a binary code associated with the RF signal, a motion detector for sensing the intrusion and a volatile memory for recording the occurrence of either the intrusion or an interruption of power to the monitor. As taught by Carney, the volatile memory circuit is switched from an armed state to a disarmed state by either the sensing of an intrusion or by an interruption of the primary power. The code stored in the nonvolatile memory is not effected by either a momentary or a sustained power interruption. When the volatile memory circuit is in the armed state, the monitor produces a response to an RF test signal transmitted by the remote controller. If the monitor has sensed an intrusion or a power failure and the volatile memory circuit has been switched to the disarmed state, the monitor does not respond, thus warning the returning occupant not to reenter his or her premises. However, Carney does not teach a means by which to prevent momentary power interruptions that may occur on the AC power line from prompting the volatile memory to falsely record the same as a power interruption caused as a result of an intrusion.
U.S. patent application Ser. No. 09/547,053 filed by William P. Carney on Apr. 10, 2000 teaches a remotely accessed intrusion detection system. The system includes a self-contained monitor energized by a primary power source comprising a battery pack and/or a power jack for receiving an AC adaptor cord. In one aspect of the disclosure, Carney teaches a remote controller for arming, disarming and testing the monitor. The self-contained monitor transmits an RF monitor signal to an interface module communicating with a telephone answering machine recording the occurrence of the alarm condition thereon. A user calls the answering machine from a telephone at a distant location to receive a recorded report from the answering machine regarding the alarm condition. Carney does not address the problems associated with momentary power interruptions associated with the AC power line energizing the self-contained monitor and the possibility of such interruptions resulting in the reporting of erroneous alarm conditions by the self-contained monitor.
As can be seen from the foregoing, remotely controlled self-contained monitors offer a cost effective and reliable means by which to surveil a predetermined space and report the occurrence of an intrusion therein. Nevertheless, to optimize the reliability of the test reports produced by such self-contained monitors, there is a need in the industry to provide a self-contained monitor which does not mistakenly record momentary power line faults on an AC line energizing the monitor as power interruptions of the type which typically occur as a result of an intrusion.
The present invention is directed to a system that solves the problem of providing a cost effective and reliable means by which a user can employ a self-contained monitor powered by a primary power source to surveil a predetermined space and report the occurrence of an intrusion therein. The self-contained monitor may be remotely tested for the occurrence without concern that an erroneous intrusion report was generated as a result of a momentary power interruption associated with the primary power source.
The present invention is an improved intrusion detection system of the type a self-contained monitor surveiling a predetermined space for detecting an occurrence of an intrusion in the space. The intrusion detection system employs a primary power source energizing the self-contained monitor including a volatile memory circuit having an armed state and a disarmed state communicating with a nonvolatile memory circuit having a tuning code stored therein. The volatile memory circuit is switched from the disarmed state to the armed state by an arming signal which is qualified by the tuning code and is switched from the armed state to the disarmed state by a sensing of an interruption of primary power thereto. The improvement comprises the volatile memory circuit sensing only the interruption of primary power having a duration longer than a preset period of time and a short term energy storage circuit communicating with the primary power source and the volatile memory circuit supplying secondary power thereto such that the volatile memory circuit does not sense the interruption of primary power during the preset period of time.